Glass cutting systems and methods using non-diffracting laser beams

ABSTRACT

Embodiments are directed to systems for laser cutting at least one glass article comprising a pulsed laser assembly and a glass support assembly configured to support the glass article during laser cutting within the pulsed laser assembly, wherein the pulsed laser assembly comprise at least one non-diffracting beam (NDB) forming optical element configured to convert an input beam into a quasi-NDB beam; and at least one beam transforming element configured to convert the quasi-NDB beam into multiple quasi-NDB sub-beams spaced apart a distance of about 1 μm to about 500 μm; wherein the pulsed laser assembly is oriented to deliver one or more pulses of multiple quasi-NDB sub-beams onto a surface of the glass article, wherein each pulse of multiple quasi-NDB sub-beams is operable to cut a plurality of perforations in the glass article.

This application claims the benefit of priority under 35 U.S.C. §119 ofU.S. Provisional Application Ser. No. 62/087,406 filed on Dec. 4, 2014the content of which is relied upon and incorporated herein by referencein its entirety.

TECHNICAL FIELD

Embodiments of the present disclosure are generally related to glasscutting systems and methods, and are specifically related to glasscutting systems and methods which utilize multiple non-diffractingsub-beams.

BACKGROUND

Focused short-pulsed laser beams are used for cutting and modifyingtransparent substrates, such as glass, through the process of nonlinearabsorption via multi-photon ionization and subsequent ablation. Suchlaser systems must thus deliver a very small spot size and have highrepetition rates in order to process materials at significant speeds.Typically laser processing has used Gaussian laser beams. The tightfocus of a laser beam with a Gaussian intensity profile has a Rayleighrange Z_(R) given by:

$\begin{matrix}{Z_{R} = \frac{\pi \; n_{o}w_{o}^{2}}{\lambda_{o}}} & (1)\end{matrix}$

The Rayleigh range represents the distance over which the spot sizew_(o) of the beam will increase by √{square root over (2)} in a materialof refractive index n_(o) at wavelength λ₀. This limitation is imposedby diffraction. As shown in Eqn. 1 above, the Rayleigh range is relateddirectly to the spot size, thus a tight focus (i.e. small spot size)cannot have a long Rayleigh range. Thus, the small spot size ismaintained for an unsuitably short distance. If such a beam is used todrill through a material by changing the depth of the focal region, therapid expansion of the spot on either side of the focus will require alarge region free of optical distortion that might limit the focusproperties of the beam. Such a short Rayleigh range also requiresmultiple pulses to cut through a thick sample.

Another approach to maintaining a tightly focused beam in a material isto use nonlinear filamentation via the Kerr effect, which yields aself-focusing phenomenon. In this process, the nonlinear Kerr effectcauses the index at the center of the beam to increase, thereby creatinga waveguide that counteracts the diffraction effect described above. Thebeam size can be maintained over a much longer length than that given inEq. 1 above and is no longer susceptible to surface phase distortionsbecause the focus is defined at the surface. To produce a sufficientKerr effect, the power of the incident laser beam must exceed a criticalvalue given by equation 2 below:

$\begin{matrix}{P_{Cr} = \frac{3.72\; \lambda_{o}^{2}}{8\; \pi \; n_{o}n_{2}}} & (2)\end{matrix}$

where n₂ is the second-order nonlinear refractive index.

Despite the benefit of this extended focal range, generating beams inaccordance with the Kerr effect undesirably requires much more powerthan the above described Gaussian beam approach.

Accordingly, there is a continual need for a beam generation method in alaser cutting system which achieves a beam(s) having a controlled spotsize, longer focal length, while minimizing power requirements andincreasing process speed.

SUMMARY

Embodiments of the present disclosure are directed to glass cuttingsystems and methods for cutting glass articles optical non-diffractingbeams (NDB), specifically “complex” NDB beams having multiple-NDBsub-beams. This approach maintains the high intensities required tosustain the multi-photon absorption, and achieves beam propagation for aconsiderable distance before diffraction effects inevitably limit thebeam focus. Additionally, the central lobe of the beam can be quitesmall in radius, and thus produce a high intensity beam with acontrolled spot size. The approach of using NDBs combines the benefitsof the lower power associated with a Gaussian beam approach and the longfocal range achieved by the filamentation process (Kerr effect).

Moreover, the present NDB embodiments may advantageously increaseprocess speeds and lower operating costs, because it minimizes thenumber of pulses to cut through a substrate. The present optical systemproduces multiple simultaneous sub-beams from a single input beam pulseand thereby creates multiple damage spots or holes in a glass articlefrom each pulse. A significant improvement in the cutting speed may beachieved when compared to a single beam method which delivers only onedamage spot per pulse. (See FIG. 11 above)

According to one embodiment, a system for laser cutting at least oneglass article is provided. The system comprises a pulsed laser assemblyand a glass support assembly configured to support the glass articleduring laser cutting within the pulsed laser assembly. The pulsed laserassembly comprises at least one quasi-NDB beam forming optical elementconfigured to convert an input beam into a quasi-NDB beam, and at leastone beam transforming element configured to convert the quasi-NDB beaminto multiple quasi-NDB sub-beams spaced apart a distance of about 1 μmto about 500 μm. The pulsed laser assembly is oriented to deliver one ormore pulses of multiple quasi-NDB sub-beams onto a surface of the glassarticle, wherein each pulse of multiple quasi-NDB sub-beams is operableto cut a plurality of perforations in the glass article.

According to another embodiment, a method of laser cutting a glassarticle is provided. The method comprises feeding at least one glassarticle to a pulsed laser system that produces multiplequasi-non-diffracting beams (NDB) spaced apart a distance of about 1 μmto about 500 μm for every pulse, laser cutting the at least one glassarticle using the multiple quasi-NDB beams to achieve a plurality ofperforations in the glass article, and separating the glass articlealong the perforations to yield a laser cut glass article.

According to yet another embodiment, another system for laser cutting atleast one glass article is provided. The system comprises a pulsed laserassembly and a glass support assembly configured to support the glassarticle during laser cutting within the pulsed laser assembly. Thepulsed laser assembly comprises at least one axicon configured toconvert an input beam (e.g., a Gaussian beam) into a Bessel beam, firstand second collimating lenses disposed downstream of the axicon, and atleast one beam transforming element oriented between the first andsecond collimating lenses. The at least one beam transforming element isconfigured to convert the Bessel beam into multiple sub-Bessel beamswhich are parallel and spaced apart a distance of about 1 μm to about500 μm. The pulsed laser assembly is oriented to deliver one or morepulses of multiple sub-Bessel beams onto a surface of the glass article,wherein each pulse of multiple sub-Bessel beams is operable to cut aplurality of perforations in the glass article. In one or moreembodiments, the beam transforming element may be disposed proximate aFourier-transform plane generated by the first collimating lens ororiented within a focal length of the second collimating lens.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description of specific embodiments of thepresent disclosure can be best understood when read in conjunction withthe drawings enclosed herewith.

FIG. 1 is a schematic view of a Gaussian beam passing through the axiconto produce a quasi-NDB Bessel beam.

FIG. 2A is a schematic view of a glass cutting system in accordance withone or more embodiments of the present disclosure.

FIG. 2B is a close-up view of FIG. 2A depicting the laser cutting of theglass article in accordance with one or more embodiments of the presentdisclosure.

FIG. 3A is a graphical illustration of a computer simulation, thegraphical illustration depicting a single-axis scan across the center oftwo Bessel sub-beams separated by 5.84 μm.

FIG. 3B is a graphical illustration of a computer simulation, thegraphical illustration depicting a two-dimensional cross-section of thetwo Bessel sub-beams of FIG. 3A.

FIG. 4A is a graphical illustration of a computer simulation, thegraphical illustration depicting a single-axis scan across the center oftwo Bessel sub-beams separated by 3.23 μm, wherein a π phase shift isadded to one beam.

FIG. 4B is a graphical illustration of a computer simulation, thegraphical illustration depicting a two-dimensional cross-section of thetwo Bessel sub-beams of FIG. 4A.

FIG. 5A is a graphical illustration of a computer simulation, thegraphical illustration depicting a single-axis scan across the center ofthree Bessel sub-beams separated by 5.85 μm.

FIG. 5B is a graphical illustration of a computer simulation, thegraphical illustration depicting a two-dimensional cross-section of thethree Bessel sub-beams of FIG. 5A.

FIG. 6A is a graphical illustration of a computer simulation, thegraphical illustration depicting a single-axis scan across the center ofthree Bessel sub-beams separated by 3.23 μm, wherein a π phase shift isadded to one beam.

FIG. 6B is a graphical illustration of a computer simulation, thegraphical illustration depicting a two-dimensional cross-section of thethree Bessel sub-beams of FIG. 6A.

FIG. 7 is a schematic depiction of an optical assembly used in thepulsed laser assembly wherein the beam transforming element is orientedproximate the Fourier-transform plane of an upstream collimating lensaccording to one or more embodiments of the present disclosure.

FIG. 8 is a schematic depiction of an optical assembly used in thepulsed laser assembly wherein the beam transforming element is orientedwithin a focal length of a downstream collimating lens according to oneor more embodiments of the present disclosure.

FIG. 9 is a schematic depiction of an alternative optical assembly withsmaller optical elements according to one or more embodiments of thepresent disclosure.

FIG. 10 is a schematic depiction of yet another optical assembly with areflective optical element according to one or more embodiments of thepresent disclosure.

FIG. 11 is a schematic depiction comparing damage spots produced by one,two, and three beam systems.

The embodiments set forth in the drawings are illustrative in nature andnot intended to be limiting of the invention defined by the claims.Moreover, individual features of the drawings will be more fullyapparent and understood in view of the detailed description.

DETAILED DESCRIPTION

Referring to the embodiments of the FIGS. 2A and 2B, a system 1 forlaser cutting at least one glass article is shown. The system 1comprises a pulsed laser assembly 10 and a glass support assembly 50which supports the glass article 5 during laser cutting by the pulsedlaser assembly 10. As shown in FIGS. 2A and 2B, the pulsed laserassembly 10 delivers one or more pulses of multiple quasi-NDB sub-beams18A, 18B onto a surface of the glass article 5. Referring to FIG. 2B,the pulse (or complex beam) 18 of multiple quasi-NDB sub-beams 18A, 18Bmay cut a plurality of perforations 6A, 6B or in the glass article 5. Asshown in the embodiment of FIG. 2A, the glass support assembly 50 ismerely depicted as a conveyor; however, various other components such asa spindle chuck, robotic arm, etc are contemplated as suitable herein.These contemplated embodiments may cause the pulsed laser assembly 10and the glass support assembly 50 to be moveable relative to one anotherduring the laser cutting process.

Referring to FIG. 7, the pulsed laser assembly 10 comprises at least oneNDB forming optical element 20 that converts an input beam 7 (e.g., aGaussian beam) into a quasi-NDB beam 12 (See also FIG. 1), and at leastone beam transforming element 40 which converts the quasi-NDB beam 12into multiple quasi-NDB sub-beams 18A, 18B, 18C spaced apart a distanceof about 1 μm to about 500 μm.

As used herein, “quasi-NDB beam” means a created non-diffracting beam,typically a nondiffracting beam created from the conversion of an inputbeam (e.g., a Gaussian beam) to a non-diffracting beam. The quasi-NDBbeam could encompass many beam types. As used herein, “input beam” mayinclude any beam having a substantially uniform optical phase. In oneembodiment, the input beam is a Gaussian beam. For example, thequasi-NDB may include a Bessel beam, an Airy beam, a Weber beam, or aMathieu beam. In the embodiments described below, the quasi-NDB beam isa Bessel beam. The conversion of a Gaussian beam 7 by an axicon NDBforming optical element 20 to a Bessel quasi-NDB beam 12 is shown inFIG. 1. FIG. 1 depicts a single pulse Gaussian beam; however, theGaussian beam source may also deliver the Gaussian beam in multiplepulses. In addition to axicons, various other NDB forming opticalelements are contemplated, for example, a spatial light modulator, anelliptical lens, or combinations thereof. Bessel beams may be readilyproduced by axicons; however, other quasi-NDB beams are produced withother NDB forming elements 20.

Further as used herein, “multiple quasi-NDB sub-beams” does not meanseparate NDB laser beams. “Multiple quasi-NDB sub-beams” means a complexbeam having a plurality of spots. Referring to FIG. 3A, the two peaks18A and 18B are two quasi-NDB sub-beams in the complex Bessel beamdepicted therein. As shown in FIG. 1, Bessel beams tend to have acentral peak at zero, which would constitute its beam spot. However, inaccordance with the present embodiments, the Bessel beam is converted inthe beam transforming element 40, such that the Bessel beam with asingle spot is transformed into a modified Bessel beam having two spotscorresponding to peaks 18A and 18B. These two spots or two quasi-NDBsub-beams are depicted in cross-section in FIG. 3B. FIGS. 4A and 4Bdepict another embodiment having 2 quasi-NDB sub-beams, and FIGS. 5A-6Bdepict embodiments with 3 quasi-NDB sub-beams 18A, 18B, and 18C. Whilenot shown, “multiple quasi-NDB sub-beams” encompasses complex beamshaving more than 2 or 3 quasi-NDB sub-beams.

Referring to FIGS. 7 and 8, the beam transforming element 40 converts aquasi-NDB beam 12 into multiple quasi-NDB sub-beams 18A, 18B, and 18C.The beam transformation essentially re-shapes the high intensity singlequasi-NDB beam into multiple lower intensity sub-beams, which in mostembodiments are spaced apart from one another. As shown in FIGS. 3A-6B,the multiple quasi-NDB sub-beams are depicted as being in parallel;however, it is contemplated that the multiple quasi-NDB sub-beams 18could be angled such that they overlap with one another. In addition togenerating the multiple quasi-NDB sub-beams, the beam transformingelement 40 may optimize the spacing between the beams, and optionallymay shift the phase of one or more of the multiple quasi-NDB sub-beams.By phase shifting the phase of at least one of the multiple quasi-NDBsub-beams, the intensity of the multiple quasi-NDB sub-beams may beadded coherently. Depending on the glass cutting application, variousspacings between sub-beams may be sought. For example, the spacing maybe from about 1 μm to about 500 μm, or about 1 μm to about 200 μm, orabout 1 μm to about 100 μm, or about 1 μm to about 50 μm, or about 1 μmto about 20 μm, or about 1 μm to about 10 μm, or about 1 μm to about 5μm. Similarly, the degree of phase shift may vary with phase shiftsranging from about π/4 to about 2π, or about π/2 to about π beingcontemplated.

The beam transforming element 40 may comprise various components. Forexample and not by way of limitation, the beam transforming elements maycomprise is a phase grating or phase plate, an amplitude grating, orcombinations thereof. In specific embodiment, it may be beneficial toinclude a beam transforming element 40 which is a combination of a phaseelement and an amplitude element. These gratings may be square wave orsinusoidal; however, other complex shapes are contemplated herein. Afurther discussion of beam transforming elements 40 is provided below.

An amplitude-only grating may be defined by the following equation:

$\begin{matrix}{{P_{tot}\left( {u,v} \right)} = {0.5 + {0.5*{\cos \left( \frac{2\; \pi \; u}{T} \right)}}}} & (3)\end{matrix}$

Physically, this would be a much easier grating to make, because nophase shift is required; however, such a grating may produces many orderbeams, for example, a zeroth-order beam and two first-order beams. Thus,in some embodiments, a phase shift may be utilized to substantiallylimit the beams to a single order.

Phase-only gratings may be formed from a thickness or index grating inglass or using a programmable spatial light modulator. A squarephase-only grating can more efficiently couple light into the sub-beams.For two beams, the most efficient phase-only grating may be defined by:

$\begin{matrix}{{P_{tot}\left( {u,v} \right)} = e^{i\; \varphi_{o}{{rect}{(\frac{2\; \pi \; u}{T})}}}} & (4)\end{matrix}$

Where

$\varphi_{o} = {\frac{\pi}{2}\mspace{14mu} {and}\mspace{14mu} {rect}\mspace{11mu} \left( \frac{2\; \pi \; u}{T} \right)}$

is a square-wave function of u oscillating between −1 and +1 with aperiod of T. With the square grating, additional diffraction orders maybe present, but with the correct choice of phase amplitude they can beminimized. With the sinusoidal amplitude grating, there are only the twofirst-order beams.

To generate a third beam, it is possible to use

$\varphi_{o} = {\left. {{atan}\left( \frac{\pi}{2} \right)} \right.\sim 1}$

rad to give:

$\begin{matrix}{{P_{tot}\left( {u,v} \right)} = e^{{irect}{(\frac{2\; \pi \; u}{T})}}} & (5)\end{matrix}$

which results in three beams.

In one or more embodiments, static phase elements can be made to variousscales. However, it may be desirable to use programmable phase elementssuch as acousto-optic modulators (AOM), electro-optic modulators (EOM),spatial light modulators (SLM) and digital micro-mirror arrays (DMA).

Without being bound by theory, sub-beam spacings that preserve thecharacteristics of the input beam 7 are beneficial. As an example, adiscussion regarding combining two zeroth-order Bessel beams is providedbelow. This approach can be used for finding the optimal spacings forother quasi-NBD sub-beams.

As shown in FIG. 1, the Bessel function J₀(x) is an oscillatory function(positive and negative) about zero. If two Bessel functions are addedcoherently with a lateral offset, they will interfere destructively whena positive peak in one function overlaps with a negative peak in thesecond function. Similarly, the beams will add constructively when twopositive peaks add. The locations of the positive maxima and negativeminima of the function J₀(x) are given by the zeros of the higher-orderBessel function J₁(x) (through a well-known relationship thatdJ₀(x)/dx=−J₁(x)). These zeros β_(j) are well known and the first feware given in Table 1 below. For roots beyond those shown in Table 1, theroots become equally spaced by ·π, so simply add multiples of π=3.14159to the 7^(th) root.

The equation for optimal Δx_(opt) that optimizes the peak intensity ofthe sub-beams may be defined as:

$\begin{matrix}{{{\Delta \; x_{{opt},j}} = \frac{\beta \; j}{k_{r}}}{{where}\text{:}}} & (6) \\{k_{r} = {{k \cdot {NA}} = {{\frac{2\; \pi \; n_{o}}{\lambda_{o}} \cdot \sin}\; {(\beta).}}}} & (7)\end{matrix}$

For λ₀=1.06 μm in air with numerical aperture (NA)=0.2 (or β=11.5°), wefind k_(r)=1.1855 μm⁻¹ and the resulting optimal spacing is given in the4^(th) column of Table 1 while column 5 gives the spacing for NA=0.1(narrow cone angle of β=5.7°). When the beams are added with no phaseshift between them, we use the odd roots j=3, 5, etc.

An alternative approach for generating two beams would be to add the twocoherent beams with a phase shift between them. If we add a π shift tothe relative optical phase, this is equivalent to multiplying one of thebeams by a minus sign. Thus the positive peaks of one beam will addcoherently to the negative peaks of the second beam. This allows forefficient beam separations at the spacings labeled “N” in the thirdcolumn of Table 1, corresponding to the even roots j=2, 4, etc.

TABLE 1 Example Δx_(opt) Example Δx_(opt) (μm) (μm) j^(th) J1 zero, NA =0.2 NA = 0.1 Root β_(j) Peak sign k_(r) = 1.1855 μm⁻¹ k_(r) = 0.5928μm⁻¹ 1 0 P 0.00 0.00 2 3.8317 N 3.23 6.46 3 7.0156 P 5.92 11.84 410.1735 N 8.58 17.16 5 13.3237 P 11.24 22.48 6 16.4706 N 13.89 27.79 719.6159 P 16.55 33.09

For illustration, FIG. 3A depicts a two spaced quasi-NDB sub-beams, andFIG. 4A shows the two spaced quasi-NDB sub-beams but with a π phaseshifted added to one of the beams. Both FIGS. 3A and 4A show optimalseparations for which the sub-beam very close together (˜3 microns).This is important in the cutting of transparent substrates for creatingnearly continuous damage zones. Similarly, FIG. 5A depicts three spacedquasi-NDB sub-beams 18A, 18B, and 18C, and FIG. 6A shows three spacedquasi-NDB sub-beams but with a π phase shifted added to the central beam18B.

For non-optimal spacing, the peak intensity is not maximized, but suchspacings may still produce acceptable cutting behavior as long assufficient laser power is available to achieve nonlinear materialdamage.

Referring to the embodiments of FIG. 7-10, specific optical assembly 11arrangements for the pulsed laser assembly 10 are depicted therein. Asshown in FIGS. 7 and 8, the optical assembly 11 may comprise at leastone collimating lens 31 configured to narrow the quasi-NDB beam 12 fromthe at least one NDB forming optical element 20.

Further as shown in FIG. 7, the beam transforming element 40 may beoriented downstream of the collimating lens 31. In a further embodiment,the beam transforming element 40 may be oriented proximate aFourier-transform plane 41 produced by the collimating lens 31. It isalso contemplated to place the beam transforming element 40 at alocation not proximate or within the Fourier-transform plane 41.Moreover as shown in FIG. 7, the optical assembly 11 may furthercomprise at least one additional collimating lens 32 downstream of thebeam transforming element 40 which focus the multiple quasi-NDBsub-beams 18A, 18B, and 18C.

Referring again to the embodiment of FIG. 7, when the beam transformingelement 40 is oriented behind the Fourier-transform plane 41 ofcollimating lens 31, the field A(u,v) at Fourier-transform plane 41 ismultiplied by a transfer function P(u,v) to produce a new field A′(u,v)with two new angular components which are then imaged by collimatinglens 32 to an image plane 17 to produce three quasi NDB sub-beams 18A,18B, and 18C. The rays after beam transforming element 40 are depictedwith dashed lines to indicate that the optical field in this region is afunction beam transforming element 40

As shown in the embodiment of FIG. 7, the focus 8 of the input beam 7 isplaced in front of the first collimating lens 31 at a distance f₁, wheref₁ is the focal length of the first collimating lens 31. A second lens32 with a second focal length f₂ is placed a distance of f₁+f₂ behindthe first lens 31. The Fourier-transform plane 41 at a distance of f₁behind the first lens 31 is the Fourier-transform plane of the firstlens 31 and the optical field at this plane is known to be the opticalFourier transform A(u,v) of the input field a(x,y) at a distance f₁ infront of collimated lens 31:

$\begin{matrix}{{A\left( {u,v} \right)} = {\int{\int_{- \infty}^{\infty}{\frac{a\left( {x,y} \right)}{i\; \lambda \; f_{1}}\ e^{\frac{{- 2}\; \pi \; {ni}}{\lambda \; f_{1}}{({{xu} + {yv}})}}{x}{y}}}}} & (8)\end{matrix}$

The purpose of the second lens 32 is to take the inverse Fouriertransform of the optical field A(u,v) in Fourier-transform plane 41 andform an image b(x,y) of the input beam in image plane 17. It can beshown that:

$\begin{matrix}{{b\left( {x^{\prime},y^{\prime}} \right)} = {\int{\int_{- \infty}^{\infty}{\frac{A\left( {u,v} \right)}{i\; \lambda \; f_{2}}e^{\frac{{- 2}\; \pi \; {ni}}{\lambda \; f_{2}}{({{ux}^{\prime} + {vy}^{\prime)}}}}\ {u}{v}}}}} & \left( {9a} \right) \\{\mspace{85mu} {= {\frac{f_{1}}{f_{2}}{a\left( {{{- \frac{f_{1}}{f_{2}}}x^{\prime}},{{- \frac{f_{1}}{f_{2}}}y^{\prime}}} \right)}}}\mspace{140mu}} & \left( {9b} \right) \\{\mspace{85mu} {= {M\; {a\left( {{{- M}\; x^{\prime}},{{- M}\; y^{\prime}}} \right)}}}\mspace{166mu}} & \left( {9c} \right)\end{matrix}$

If f₁≠f₂, the image will have a magnification M≠1 and the quasi NDBsub-beams may not be parallel. If f₁=f₂, the image will have amagnification M=1 and the quasi NDB sub-beams will be parallel.

Introducing the beam transforming element 40 in the Fourier-transformplane 41 has the effect of multiplying the Fourier-transform of theinput field by the transfer function of this element:

$\begin{matrix}{{{b^{\prime}\left( {x^{\prime},y^{\prime}} \right)} = {\int{\int_{- \infty}^{\infty}{\frac{A^{\prime}\left( {u,v} \right)}{i\; \lambda \; f_{2}}e^{\frac{{- 2}\; \pi \; {ni}}{\lambda \; f_{2}}{({{ux}^{\prime} + {vy}^{\prime)}}}}\ {u}{v}}}}}\mspace{70mu}} & \left( {10a} \right) \\{\mspace{95mu} {= {\int{\int_{- \infty}^{\infty}{\frac{{A\left( {u,v} \right)}{P\left( {u,v} \right)}}{i\; \lambda \; f_{2}}e^{\frac{{- 2}\; \pi \; {ni}}{\lambda \; f_{2}}{({{ux}^{\prime} + {vy}^{\prime)}}}}\ {u}{v}}}}}} & \left( {10b} \right)\end{matrix}$

It is known that certain optical elements can shift an input beam in anarbitrary direction, can impart a tilt to the focal region, and canscale the amplitude of the output beam. Other elements and apertures canbe used to filter unwanted spatial frequencies from the beam in order tomitigate or create impairments to the optical beam. In this disclosure,we will focus on the lateral shifting of quasi-NDB sub-beams to generatemultiple quasi NDB sub-beams.

The phase transformation to accomplish a lateral shift (Δx,Δy) is:

$\begin{matrix}{{P\left( {u,v} \right)} = e^{\frac{2\; \pi \; {ni}}{\lambda \; f_{2}}{({{u\; \Delta \; x^{\prime}} + {v\; \Delta \; y^{\prime}}})}}} & (11)\end{matrix}$

From above it can be seen that:

$\begin{matrix}{{{b^{\prime}\left( {x^{\prime},y^{\prime}} \right)} = {\int{\int_{- \infty}^{\infty}{\frac{{A\left( {u,v} \right)}{P\left( {u,v} \right)}}{i\; \lambda \; f_{2}}e^{\frac{{- 2}\; \pi \; {ni}}{\lambda \; f_{2}}{({{ux}^{\prime} + {vy}^{\prime)}}}}\ {u}{v}}}}}\mspace{65mu}} & \left( {12a} \right) \\{\mspace{95mu} {= {\int{\int_{- \infty}^{\infty}{\frac{A\left( {u,v} \right)}{i\; \lambda \; f_{2}}e^{\frac{2\; \pi \; {ni}}{\lambda \; f_{2}}{({{u\; \Delta \; x} + {v\; \Delta \; y^{)}}}}}e^{\frac{{- 2}\; \pi \; {ni}}{\lambda \; f_{2}}{({{u\; x^{\prime}} + {v\; {y^{\prime}}^{)}}}}}{u}{v}}}}}} & \left( {12b} \right) \\{\mspace{95mu} {= {M\; a\left\{ {{- {M\left( {x^{\prime} - {\Delta \; x}} \right)}},{- {M\left( {y^{\prime} - {\Delta \; y}} \right)}}} \right\}}}\mspace{160mu}} & \left( {12c} \right)\end{matrix}$

Thus, the output field b′(x′,y′) in image plane 17 is a scaled andshifted version of the input field a(x,y).

It is also known that multiple quasi-NDB sub beams can be produced bysumming different phase shifts:

$\begin{matrix}{{P_{tot}\left( {u,v} \right)} = {\frac{1}{\sum\limits_{j = 1}^{N}\; {c_{j}}}{\sum\limits_{j = 1}^{N}\; {c_{j}e^{\frac{2\; \pi \; n\; i}{\lambda \; f_{2}}{({{u\; \Delta \; {x\;}_{j}} + {v\; \Delta \; {y\;}_{j}}})}}}}}} & (13)\end{matrix}$

For the special case of two equal beams, N=2 spaced by x_(o):

$\begin{matrix}{{P_{tot}\left( {u,v} \right)} = {\frac{1}{2}\left\lbrack {e^{\frac{2\; \pi \; {ni}}{\lambda \; f_{2}}{({u\frac{\Delta \; x_{0}}{2}})}} + e^{\frac{{- 2}\; \pi \; {ni}}{\lambda \; f_{2}}{({u\frac{\Delta \; x_{0}}{2}})}}} \right\rbrack}} & \left( {14a} \right) \\{\mspace{101mu} {= {\cos \; \left( {\frac{2\; {\pi n}}{\lambda \; f_{2}}\left( {u\frac{\Delta \; x_{0}}{2}} \right)} \right)}}\mspace{121mu}} & \left( {14b} \right) \\{\mspace{95mu} {= {\cos \left( \frac{2\; \pi \; u}{T} \right)}}\mspace{200mu}} & \left( {14c} \right)\end{matrix}$

where

$T = {\frac{2\; \lambda \; f_{2}}{n\; \Delta \; x_{0}}.}$

In this instance, P_(tot)(u,v) is simply a cosinusoidal amplitudediffraction grating of period T. When a phase shift is introducedbetween the two beams we find:

$\begin{matrix}{{P_{tot}\left( {u,v} \right)} = {\frac{1}{2}\left\lbrack {{e^{i\; \varphi}e^{\frac{2\; \pi \; n\; i}{\lambda \; f_{2}}{({u\frac{\Delta \; x_{0}}{2}})}}} + e^{\frac{{- 2}\; \pi \; n\; i}{\lambda \; f_{2}}{({u\frac{\Delta \; x_{0}}{2}})}}} \right\rbrack}} & \left( {15a} \right) \\{\mspace{95mu} {= {\cos \left( {\frac{2\; \pi \; u}{T} + \frac{\varphi}{2}} \right)}}\mspace{185mu}} & \left( {15b} \right)\end{matrix}$

So that a phase shift of φ=π between the sub-beams adds a phase of φ/2to the cosine which makes it a sine function. Practically, thiscorresponds to a lateral shift of the grating by a quarter of a periodor T/4.

In addition to the arrangement of FIG. 7, the NBD forming opticalelement 20 (e.g., axicon) may be at a distance greater or less than thefocal length f1 of lens 31. This may lead to an uncollimated regionbetween the collimating lenses 31 and 32, and thus may impact the choiceof the beam transforming element 40. Additionally, various distances arecontemplated between collimating lenses 31 and 32. For example, thedistance between collimating lenses 31 and 32 differ may be greater orless than f1+f2.

Alternatively, the embodiments above describe the positioning of thebeam transforming element 40 after lens 31; however, various otherpositions are also contemplated. For example, and not by way oflimitation, the beam transforming element 40 may be positioned beforecollimating lens 31 or after collimating lens 32.

Various additional optical assemblies are also contemplated herein. Inthe embodiment of FIG. 8, the optical assembly may also include the beamtransforming element 40 within the focal length (f₂) of collimating lens32, which is downstream of the beam transforming element 40. As shown,this may be achieved by placing the beam transforming element 40 inclose proximity to collimating lens 31, which is upstream of the beamtransforming element 40.

In an additional embodiment depicted in FIG. 9, the optical assembly 11may comprise comprising multiple collimated regions 30 and 35. In theembodiment of FIG. 9, the multiple collimated regions 30 and 35 includea large collimated region 30 and a small collimated region 35 downstreamof the large collimated region 30. The large collimated region 30 mayinclude one or multiple collimating lenses 31 and 32 that narrow the NDBbeam from the at least one NDB forming optical element 20. Moreover, theoptical assembly 11 may include a small collimated region 35 downstreamof the large collimated region 30 which narrows the quasi-NDB beam fromthe prior to splitting in the beam transforming element 40. The smallcollimated region 35 includes one or a plurality of collimating lenses36 and 37. While the beam transforming element 40 is disposed in thesmall collimated region 35 in the embodiment of FIG. 9, it iscontemplated that the beam transforming element 40 may be disposed inthe large collimated region 30.

Without being bound by theory, having two collimating regions 30 and 35as shown in FIG. 9 is useful to accommodate a Bessel beam Rayleigh rangeoptimized for large diameter beams with large numerical apertures. Forexample, the diameter of the beam between collimating lens 31 andcollimating lens 32 is large e.g., 10-30 mm. Thus, to provide smallfocal spots, it may be necessary to include the small collimated region35 that is small in diameter.

Referring to FIG. 10, an alternative optical assembly may include areflective beam transforming element 40. In this instance, after theinput beam 7 is converted by an axicon 20 into a quasi-NDB beam 12, itis linearly polarized and passes through a polarizing beam splitter 48in the collimating region between collimating lenses 31 and 32. Thequasi-NDB beam 12 then passes through a quarter wave plate 46 to becomecircularly polarized before being recollimated with demagnification bycollimating lenses 32 and 33. The quasi-NDB beam 12 is converted intomultiple quasi-NDB-beams, which are then retroreflected off thereflective beam transforming element 40 and back through collimatinglenses 33 and 32. The multiple quasi-NDB-beams are further rotated inpolarization by the quarter wave plate 46 and thereby achieve theopposite linear polarization to input beam 7. This new polarization isreflected by beam splitter 48 and the beam is focused to its final sizeby collimating lens 38.

As stated above, it is also anticipated that the optical assemblies mayhave apertures to block unwanted light from reaching the image plane 17.This may be the case with phase only gratings that have higher-orderdiffraction patterns. The magnification of the final image is dependenton the choice of focal lengths. Without being bound by theory, thetarget beam spacing is specified in the image plane and can thus betuned by both the grating and the optical magnification.

Turning now to glass cutting applications, the present embodiments mayyield improved formation of single lines of damage (i.e., perforations)and improved formation of multiple lines to form arrays of damage sites.

In the case of the single damage line, the multiple sub-beams arealigned with the scan direction of the laser. For example, if a 100 kHzlaser system is used to create damage sites spaced at 3 microns, asingle beam optical system could be scanned 3 microns every 10microseconds for a cutting speed of 0.5 m/s. However, with 3 sub-beams,the same system could run at 1.5 m/s by moving the compound beam spot by9 microns in the same 10-microsecond time interval.

In the case of the multiple damage lines for array applications asdepicted in FIG. 11, the multiple sub-beams are aligned orthogonally tothe scan direction of the laser. For example as depicted in FIG. 11, ifa 100 kHz laser system is used to create a 10,000×10,000 damage sitesspaced at 10 microns, a single beam optical system would require 1000seconds to create the array. A three sub-beam system could finish thesame task in 334 seconds.

As would be familiar to one of skill in the art, various othercomponents are contemplated for the laser cutting assembly. For example,the laser cutting assembly may include some mechanism for separating theglass article along the perforations to yield a laser cut glass article.This may include thermal shock devices, cracking beams, etc.

It is further noted that terms like “preferably,” “generally,”“commonly,” and “typically” are not utilized herein to limit the scopeof the claimed invention or to imply that certain features are critical,essential, or even important to the structure or function of the claimedinvention. Rather, these terms are merely intended to highlightalternative or additional features that may or may not be utilized in aparticular embodiment of the present disclosure.

It will be apparent that modifications and variations are possiblewithout departing from the scope of the disclosure defined in theappended claims. More specifically, although some aspects of the presentdisclosure are identified herein as preferred or particularlyadvantageous, it is contemplated that the present disclosure is notnecessarily limited to these aspects.

What is claimed is:
 1. A system for laser cutting at least one glassarticle comprising a pulsed laser assembly and a glass support assemblyconfigured to support the glass article during laser cutting within thepulsed laser assembly, wherein the pulsed laser assembly comprises atleast one non-diffracting beam (NDB) forming optical element configuredto convert an input beam into a quasi-NDB beam; and at least one beamtransforming element configured to convert the quasi-NDB beam intomultiple quasi-NDB sub-beams spaced apart a distance of about 1 μm toabout 500 μm; wherein the pulsed laser assembly is oriented to deliverone or more pulses of multiple quasi-NDB sub-beams onto a surface of theglass article, wherein each pulse of multiple quasi-NDB sub-beams isoperable to cut a plurality of perforations in the glass article.
 2. Thesystem of claim 1 further comprising at least one collimating lensconfigured to narrow the quasi-NDB beam from the at least one NDBforming optical element.
 3. The system of claim 2 wherein the beamtransforming element is oriented downstream of the collimating lens. 4.The system of claim 3 wherein the beam transforming element is orientedproximate a Fourier-transform plane produced by the collimating lens. 5.The system of claim 1 further comprising at least one additionalcollimating lens downstream of the beam transforming element andconfigured to focus the multiple quasi-NDB sub-beams.
 6. The system ofclaim 5 wherein the beam transforming element is oriented within a focallength of the additional collimating lens.
 7. The system of claim 1wherein the input beam is a Gaussian beam.
 8. The system of claim 1wherein the multiple quasi-NDB sub-beams are parallel to one another andspaced apart a distance of about 1 μm to about 20 μm.
 9. The system ofclaim 1 wherein the beam transforming element is chosen from a phasegrating, an amplitude grating, or combinations thereof, and the NDBforming optical element is chosen from an axicon, a spatial lightmodulator, an elliptical lens, or combinations thereof.
 10. The systemof claim 1 wherein the beam transforming element is configured to shifta phase of at least one of the multiple quasi-NDB sub-beams from aboutπ/4 to about 2π.
 11. The system of claim 1 wherein the quasi-NDB beam isa Bessel beam, an Airy beam, a Weber beam, or a Mathieu beam.
 12. Amethod of laser cutting at least one glass article comprising: feedingthe at least one glass article to a pulsed laser system that producesmultiple quasi-non-diffracting beams (NDB) spaced apart a distance ofabout 1 μm to about 500 μm for every pulse; laser cutting the at leastone glass article using the multiple quasi-NDB sub-beams to achieve aplurality of perforations in the glass article; and separating the glassarticle along the plurality of perforations to yield a laser cut glassarticle.
 13. The method of claim 12 wherein the pulsed laser systemcomprises at least one NDB forming optical element configured to convertan input beam into a quasi-NDB beam, and at least one beam transformingelement configured to convert the quasi-NDB beam into the multiplequasi-NDB sub-beams.
 14. The method of claim 13 wherein the beamtransforming element is chosen from a phase grating, an amplitudegrating, or combinations thereof, and the NDB forming optical element ischosen from an axicon, a spatial light modulator, elliptical lens, orcombinations thereof.
 15. The method of claim 12 wherein a phase of atleast one of the multiple quasi-NDB sub-beams is shifted from about π/4to about 2π.
 16. A system for laser cutting at least one glass articlecomprising a pulsed laser assembly and a glass support assemblyconfigured to support the glass article during laser cutting within thepulsed laser assembly, wherein the pulsed laser assembly comprises atleast one axicon configured to convert a Gaussian beam into a Besselbeam; first and second collimating lenses disposed downstream of theaxicon; and at least one beam transforming element oriented between thefirst and second collimating lenses, wherein the at least one beamtransforming element is configured to convert the Bessel beam intomultiple sub-Bessel beams which are parallel and spaced apart a distanceof about 1 μm to about 500 μm; wherein the pulsed laser assembly isoriented to deliver one or more pulses of multiple sub-Bessel beams ontoa surface of the glass article, wherein each pulse of multiplesub-Bessel beams is operable to cut a plurality of perforations in theglass article.
 17. The system of claim 16 wherein the beam transformingelement is a phase grating, an amplitude grating, or combinationsthereof.
 18. The system of claim 16 wherein the multiple quasi-NDBsub-beams are spaced apart a distance about 1 μm to about 20 μm.
 19. Thesystem of claim 16 wherein the beam transforming element is orientedproximate a Fourier-transform plane produced by the first collimatinglens.
 20. The system of claim 16 wherein the beam transforming elementis oriented within a focal length of the second collimating lens.